Ru(II)-Catalyzed Divergent C–H Annulations of Propargyl Cyclic Carbonates

Herein, we report Ru(II)-catalyzed divergent annulations of propargyl cyclic carbonates with arylpyrazolidinones <i>via</i> C-H bond activation. The combination of base and solvent was pivotal in dictating the reaction pathway, enabling selective access to either (4+3) or (3+2) annulated nitrogen-containing heterocycles with high regioselectivity. While AgOAc in DCM promoted the three-center reactivity of propargyl carbonate, NaOAc in toluene induced two-center reactivity. Both protocols exhibited broad substrate scope and excellent functional group tolerance. The synthetic utility was demonstrated through late-stage modification of biologically active derivatives, gram-scale synthesis, and postfunctionalizations of the products to other valuable motifs.